principle: late 14c., “origin, source, beginning; rule of conduct; axiom, basic assumption; elemental aspect of a craft or discipline,” from AngloFrench principle, Old French principe “origin, cause, principle,” from Latin principium “a beginning, commencement, origin, first part,” in plural, principia, “foundation, elements,” from princeps (genitive principis) “first man, chief leader; ruler, sovereign,” noun use of adjective meaning “that takes first,” from primus “first” + root of capere “to take.”